The 29-year-old singer says he gained 30 pounds and took to Instagram early Saturday morning to share a side-by-side pic of his body transformation.
"On the left 115 on the right 145 ??Continuing to focus on myself and my health. Sorry I couldn't wait to show you till 2018 #proudofmyself #StressFree," he captioned the snap. "I missed you all so much. Needed some time to heal and this is a direct result."
Carter checked out of the health and wellness facility he was at for two weeks on Thursday night after "several legal and personal matters arose that required his immediate and in-person attention," his rep told ET on Friday. "He is still very much committed to his wellness and will be continually working toward him being the best person possible."
A source told ET that Carter had "gained a significant amount of weight and was getting stronger by the day."
Carter, who told fans on Sept. 22 that he would be staying off social media until 2018, explained on Twitter on Saturday that he had "changed my mind."
"Thank you to everyone who has continued to believe in me and stick by My side," he wrote. "I will always aim to make you proud but this was for me."